1. Priority Claim
Priority is claimed for this invention and application, a corresponding application having been filed in Europe on Apr. 2, 2002, No. 02007271.6.
2. Field of the Invention
The invention relates to a friction clutch assembly, in particular for motor vehicles, including a clutch housing, at least one first friction plate in the housing, and a second friction plate bearing the clutch housing, wherein the first pressure plate is rotationally fixed and axially displaceable with respect to clutch housing. At least one driver disk is arranged axially adjacent to the at least one first friction plate and the second friction plate and has oppositely facing friction linings which interact with the adjacent friction plates, and a spring loads the at least one friction plate toward the second friction plate. 3. Description of the Related Art
In friction clutches of this type, it is preferable to use organically bonded friction linings which are arranged on driver disks and act against metallic friction plates in the form of the pressure plate and the flywheel. In passenger automobile clutches, the friction material used is usually the gray cast iron designated GG, GGV or GGG. The rotating components pressure plate and flywheel, in operation, are subject to very high mechanical loads which substantially result from the centrifugal force, which is directly proportional to the material density. Gray cast iron, with a density of 7.2 kg/dm3, has a limited strength of approx. 250 MPa to 400 MPa, which is dependent on the quality. Therefore, a strength to density ratio which is relatively low and unfavorable for use as clutch material is present.
As an alternative to cast materials, if space is limited or if there are high demands on strength, for example high acceleration demands, steel is increasingly being used for one friction plate. Steel generally has a higher strength but this is partly offset by the increased density compared to gray cast iron of 7.85 kg/dm3.
The components of a friction clutch are generally to be designed in such a way that the quantity of heat which is produced when the clutch is operating can be taken up and dissipated by these components without overheating and without the frictional properties being adversely affected. The design of the friction plates used, i.e. the material thickness and therefore the mass of the components, is therefore predominantly determined by the heat capacity of the material used. Gray cast iron and steel have approximately the same heat capacity of approx. 500J·kg31 1·K−1. Lighter structures, as are increasingly required in consumption-optimized vehicles, for high-acceleration applications and for rotary inertia compensation for new types of components in the drive train, for example a starter generator or a double clutch, cannot consistently be implemented with the above-mentioned materials.
A further significant physical variable in a friction clutch is the thermal conductivity of the friction plates. Gray cast iron and steel have similar thermal conductivities at approx. 50 W·m−1K−1. With a similarly low thermal conductivity at this level, it is often not possible for the frictional heat which is produced to be dissipated sufficiently quickly from the friction region, and consequently heat may build up, in which case the temperature of the friction region can very quickly reach high levels. This effect can lead to a significant curvature (shielding) of the pressure plate and to a sudden deterioration in the friction properties (fading) and may even result in complete failure of the friction clutch.
Furthermore, gray cast iron and steel are also limited in terms of their wear resistance, which means that the use of tribologically favorable but aggressive friction linings, e.g. sintered metallic materials, on the driver disk is only permitted to a limited extent. The abrasion of a passenger automobile clutch over an assumed service life of approx. 200,000 km is approximately 0.3 to 0.5 mm.
To satisfy the high surface demands, friction plates made from gray cast iron or steel have to undergo finish machining. This operation may disadvantageously lead to distortion of the friction plate. The high manufacturing costs incurred are a further drawback.
This results in the object of proposing a friction clutch arrangement using a material which is able to satisfy the high demands imposed during operation of a friction clutch arrangement and, at the same time, results in a weight saving compared to conventional materials.